The E3 ubiquitin ligase Asb2ß is downregulated in a mouse model of hypertrophic cardiomyopathy and targets desmin for proteasomal degradation.

ABSTRACT

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is an autosomal-dominant disease with mutations in genes encoding sarcomeric proteins. Previous findings suggest deregulation of the ubiquitin proteasome system (UPS) in HCM in humans and in a mouse model of HCM (Mybpc3-targeted knock-in (KI) mice). In this study we investigated transcript levels of several muscle-specific E3 ubiquitin ligases in KI mice and aimed at identifying novel protein targets. METHODS AND RESULTS: Out of 9 muscle-specific E3 ligases, Asb2ß was found with the lowest mRNA level in KI compared to wild-type (WT) mice. After adenoviral-mediated Asb2ß transduction of WT neonatal mouse cardiomyocytes with either a WT or inactive Asb2ß mutant, desmin was identified as a new target of Asb2ß by mass spectrometry, co-immunoprecipitation and immunoblotting. Immunofluorescence analysis revealed a co-localization of desmin with Asb2ß at the Z-disk of the sarcomere. Knock-down of Asb2ß in cardiomyocytes resulted in higher desmin protein levels. Furthermore, desmin levels were higher in ventricular samples of HCM mice and patients than controls. CONCLUSIONS: This study identifies desmin as a new Asb2ß target for proteasomal degradation in cardiomyocytes and suggests that accumulation of desmin could contribute to UPS impairment in HCM mice and patients.